SERTULAEIA TUMIDA. 23 



These bands, so far as I am aware, have not been hitherto described. 

 I have found them in many other Sertularidans, and they are especially 

 obvious in young hydrothecse. They are destitute of fibrillation, and appear 

 to consist of a cord of protoplasm enclosing nucleus-like bodies, and are 

 plainly intended to close the valves forming the operculum of the hydro- 

 theca during the retreat of the hydranth. 



Specimens of the same variety, but in which the strong, robust habit 

 was still better marked, were dredged by the " Porcupine," in the eastern 

 parts of the North Atlantic* 



Genus SERTULARIA Linn^us (in part). 



Sertularia marginata. 

 PI XVI. Fi(/s. 1, 2. 

 Tropliosome. — Hydrocaulus attaining a height of about an inch, simple; 

 internodes elongated, attenuated below every pair of hydrothecoe. Hydro- 

 thecae opposite, deep, tubular, free, and divergent above for about three 

 fifths of their height, slightly tumid below ; orifice entire, with a broad rim 

 formed by close strias, which run in a circular direction round the distal 

 end of the hydrotheca. 

 Gonosome not known. 



Dredged from a depth of 324 fathoms, off Florida Reef. 



The species is remarkable for its distant pairs of long tubular hydro- 

 thecfe, with the orifice surrounded by a band of delicate circular striae. 

 The specimen is destitute of gonangia ; it is possibly immature, and may 

 become ramified before attaining its adult condition. 



Sertularia tumida. 



PI XVI. Figs. 3, 4. 



Trophosome. — Hydrocaulus attaining a height of | of an inch simple ; 

 internodes of moderate length, thinning away for some distance below 

 each pair of hydrothecae. Hydrothecoe opposite, short, tumid below, adnate 

 to the stem for about half their length, and with the distal half free and 

 diverging at nearly a right angle. 



Gonosome not known. 



Tortugas, shallow water. 



• See Report of the Hj droids collected during the Expeditions of H. M. S. Porcupine, Trans. Zobl. Soc. 

 London, 1873. 



